International law, yes, but every country that has laws basically has jurisdiction. It’s also not very well enforced. Like when the mayor of New York City (or maybe the governor, I’m not 100% sure) wanted to arrest the president/PM/dictator/whatever TF he is of Israel and turn him over to the ICC, only he looked it up and realised he didn’t actually have the authority to do that. So, of note, the ICC couldn’t just go to the US and get that terrorist dude, they needed the local authorities to do that, and, well, he’s in bed with another dictator, so that didn’t happen.

Then again, the dictator who ran that country sent his troops into another country to kidnap their leader and lock him up, so… might makes right?

Also worth noting: There are some people who believe in a world government that has jurisdiction everywhere. Most of them aren’t good people. You think they’d reign in dictators. They’d be the dictators. All the fuckers you don’t like would be running it and exerting their power over the ones you do like/tolerate. That’s why, in a nutshell, most reasonable people oppose a world government. The smaller the countries are, the more likely/probable it is/becomes that people who aren’t well served by one can just move to another (at least, this is true in some areas, like the EU, and within the US) and then the ones which make the most money will be more successful… but then some people won’t move, or can’t. But the idea is to make it easier. It’s the ones who want to control everybody and everything (you probably already know who I mean) who want a world government, with themselves in power, and the power guaranteed and be unable to be taken from them. An AskHistory comm might be better to ask about the specifics of global government vs smaller nation-states.